The Oil Shale (IMAGE) University of Bonn Caption The Oil Shale in the Messel Pit and at Eckfeld Maar also preserved many typical plants from the Eocene era. Credit © Photo: AG Wappler/Uni Bonn Usage Restrictions This photo may be used with the press release. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.